Santa Monica Bay, an important natural and economic resource for California, receives both point and nonpoint source pollution. Sport and commercial fish species living in the Bay are exposed to a variety of contaminants such as heavy metals, PCBs, and DDT. Many of these fish species are popular food items for humans, and contaminants that bioaccumulate in their tissues pose a health risk for human consumers. Metazoan parasites are commonly observed in or on fish and can be important in determining the host's general health and can also function as biomarkers of water contamination. Recent field studies have demonstrated that certain fish parasites can accumulate toxic metals from the aquatic environment at concentrations that surpass metal levels in the tissues of their hosts. Parasitic helminths are more sensitive indicators of heavy metal accumulation in fish and can provide valuable information about the risk of toxicant bioaccumulation in food fish of humans. The proposed study will quantify the relationship between metal contamination in fish and parasite tissues in three host-parasite systems in Santa Monica Bay, the helminth assemblages of Pacific sanddab, speckled sanddab, and the longfin sanddab. Sanddabs will be collected from several sites within the Bay (these sites vary in their distance from sewage outfall pipes) and from a reference site, Dana Point (contains lower levels of contaminants). Both parasite and fish tissues will be analyzed for heavy metals using atomic absorption spectrometry. The long-term objectives of this study are to incorporate parasite metal bioaccumulation into the current environmental monitoring program for Santa Monica Bay and use parasites as more sensitive indicators of pollution exposure in fish.